The invention relates to a 1-olefin isoblock polymer with long isotactic sequences and to a process for its manufacture.
It is known that polypropylene exists in various structural isomers:
(a) highly isotactic polypropylene in whose molecular chains almost all tertiary C atoms have the same configuration,
(b) isotactic stereoblock PP in whose molecular chains isotactic blocks of opposite configuration alternate regularly with one another,
(c) syndiotactic polypropylene in whose molecular chains every other tertiary C atom has the same configuration,
(d) atactic polypropylene in whose molecular chains the tertiary C atoms have a random configuration, and
(e) atactic-isotactic stereoblock PP in whose molecular chains isotactic and atactic blocks alternate with one another.
A process for the manufacture of isotactic stereoblock polymers is known in which propylene is polymerized with the aid of a metallocene of a metal of group IVb, Vb or VIb of the periodic table (q.v. U.S. Pat. No. 4,522,982). This metallocene is a mono-, di- or tri-cyclopentadienyl or substituted cyclopentadienyl compound of a metal, especially titanium. An aluminoxane is used as cocatalyst.
However, the titanocenes which are preferably used do not have sufficient heat stability in dilute solution to be usable in an industrial process. Moreover, in this process, products with longer isotactic sequences (n greater than 6) are only obtained at very low temperature (xe2x88x9260xc2x0 C.). Finally, the cocatalysts must be used in comparatively high concentration in order to achieve an adequate catalytic yield, so the catalyst residues contained in the polymer product have to be removed in a separate purification step.
It is further known that stereoblock polymers of 1-olefins with long isotactic sequences can be obtained at industrially favorable polymerization temperatures by means of a catalyst consisting of a metallocene compound with cyclopentadienyl radicals substituted by chiral groups, and of an aluminoxane (q.v. European patent application A 269987).
It is further known that stereoblock polymers of 1-olefins with a broad monomodal or multimodal molecular weight distribution can be obtained when 1-olefins are polymerized using a catalyst consisting of a chiral metallocene containing bridges and of an aluminoxane (q.v. European patent application A 269986). The polymers are particularly suitable for the production of transparent sheets.
It is also known that when a catalyst based on bis-cyclopentadienyl compounds of zirconium and on an aluminoxane is used in the polymerization of propylene, only atactic polymer is obtained (q.v. European patent application A 69951).
Finally, highly isotactic polypropylene can be manufactured by means of soluble stereorigid chiral zirconium compounds (q.v. European patent application A 185 918).
A polymerization process has been found in which a polymer of regular molecular structure and high molecular weight is obtained in high yield at industrially favorable process temperatures.
The invention thus relates to an isoblock polymer of a 1-olefin of the formula RCHxe2x95x90CH2, in which R is an alkyl radical having 1 to 28 C atoms, with molecular chains containing isotactic sequences which are separated from one another in each case by one monomer unit of opposite configuration, and with a sequence length of 3 to 50 monomer units.
The invention further relates to a process for the manufacture of the above-mentioned isoblock polymer by the polymerization of a 1-olefin of the formula RCHxe2x95x90CH2, in which R is an alkyl radical having 1 to 28 C atoms, at a temperature of xe2x88x9260 to 100xc2x0 C. and a pressure of 0.5 to 100 bar, in solution, in suspension or in the gas phase, in the presence of a catalyst consisting of a metallocene and an aluminoxane, wherein the metallocene is a compound of formula I: 
in which
M1 is a metal of group IVb, Vb or VIb of the periodic table,
R1 and R2 are identical or different and are a hydrogen atom, a C1-C10-alkyl group, a C1-C10-alkoxy group, a C6-C10-aryl group, a C6-C10-aryloxy group, a C2-C10-alkenyl group, a C7-C40-arylalkyl group, a C7-C40-alkylaryl group, a C8-C40-arylalkenyl group or a halogen atom,
R3, R4, R5 and Re are identical or different and are a hydrogen atom, a halogen atom, a C1-C10-alkyl group, xe2x80x94NR102, xe2x88x92SR10, xe2x80x94OSirR103r+1, xe2x80x94SirR103r+1 or xe2x80x94PR102, in which R10 is a halogen atom or a C1-C10-alkyl group, or pairs of adjacent radicals R3, R4, R5 and R6 form a ring with the C atoms to which they are bonded, and
R7 is 
in which
R11, R12 and R13 are identical or different and are a hydrogen atom, a halogen atom, a C1-C10-alkyl group, a C1-C10-fluoroalkyl group, a C6-C10-aryl group, a C6-C10-fluoroaryl group, a C1-C10-alkoxy group, a C2-C10-alkenyl group, a C7-C40-arylalkyl group, a C8-C40-arylalkenyl group or a C7-C40-alkylaryl group, or R11 and R12 or R11 and R13 form a ring with the atoms to which they are bonded,
M2 is silicon, germanium or tin,
p is 1, 2 or 3,
R8 and R9 are identical or different and are a groupxe2x95x90CR11R12, in which R11 and R12 are as defined above, and
m and n are identical or different and are zero, 1 or 2, m+n being zero, 1 or 2.
The isoblock polymer according to the invention is a polymer of a 1-olefin of the formula R-CHxe2x95x90CH2, in which R is an alkyl radical having 1 to 28 C atoms, preferably 1 to 10 C atoms, in particular one C atom, for example propylene, but-1-ene, hex-1-ene, 4-methylpent-1-ene or oct-1-ene. The polymer is especially a propylene polymer.
The molecular chains of this polymer contain isotactic sequences which are separated from one another in each case by one monomer unit of opposite configuration. The molecular chains preferably consist of isotactic sequences which are separated from one another in each case by one monomer unit of opposite configuration. The isotactic sequences have an average length of 3 to 50 monomer units.
As a consequence of this steric structure, the isoblock polymers according to the invention are amorphous or partly crystalline according to the molecular weight and the length of the isotactic sequences. Depending on the crystallinity, the polymers are obtained as granular powders or as compact masses. The partly crystalline isoblock polymers have a low melting point by comparison with isotactic polymers. Isoblock polymers possess rubber-like properties.
The catalyst to be used for the process according to the invention consists of a metallocene compound of formula I and an aluminoxane. In formula I: 
M1 is a metal of group IVb, Vb or VIb of the periodic table, for example titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum or tungsten, preferably zirconium or hafnium. R1 and R2 are identical or different and are a hydrogen atom, a C1-C10-, preferably C1-C3-alkyl group, a C1-C10-, preferably C1-C3-alkoxy group, a C8-C10-, preferably C6-C8-aryl group, a C6-C10-, preferably C6-C8-aryloxy group, a C2-C10-, preferably C2-C4-alkenyl group, a C7-C40-, preferably C7-C10-arylalkyl group, a C7-C40-, preferably C7-C12-alkylaryl group, a C8-C40-, preferably C8-C12-arylalkenyl group or a halogen atom, preferably chlorine.
R3, R4, R5 and R6 are identical or different, preferably different, and are a hydrogen atom, a halogen atom, preferably a fluorine, chlorine or bromine atom, a C1-C10-, preferably C1-C3-alkyl group, xe2x80x94NR102, xe2x80x94SR10, xe2x80x94OSirR103r+1, xe2x80x94SirR103r+1 or xe2x80x94PR102, in which R10 is a halogen atom, preferably a chlorine atom, or a C1-C10-, preferably C1-C3-alkyl group, or pairs of adjacent radicals R3, R4, R5 and R6 form a ring with the C atoms to which they are bonded.
R7 is 
xe2x95x90BR11, xe2x95x90AlR11, xe2x80x94Gexe2x80x94, xe2x80x94Snxe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x95x90Sxe2x95x90O, xe2x95x90SO2, xe2x95x90NR11, xe2x95x90CO, xe2x95x90PR11 or xe2x95x90P(O)R11, in which R11, R12 and R13 are identical or different and are a hydrogen atom, a halogen atom, a C1-C10-alkyl group, preferably a C1-C4-alkyl group, especially a methyl group, a C1-C10-fluoroalkyl group, preferably a CF3 group, a C8-C10-, preferably C6-C8-aryl group, a C8-C10-fluoroaryl group, preferably a hexafluorophenyl group, a C1-C10-, preferably C1-C4-alkoxy group, especially a methoxy group, a C2-C10-, preferably C2-C4-alkenyl group, a C7-C40-, preferably C7-C10-arylalkyl group, a C8-C40-, preferably C8-C12-arylalkenyl group or a C7-C40-, preferably C7-C12-alkylaryl group, or R11 and R12 or R11 and R13 form a ring together with the atoms to which they are bonded.
M2 is Si, Ge or Sn and p is 1, 2 or 3.
R7 is preferably xe2x95x90SiR11R12, xe2x95x90GeR11R12, xe2x80x94Sxe2x80x94, xe2x95x90Sxe2x95x90O or xe2x95x90PR11.
R8 and R6 are identical or different and are a group xe2x95x90CR11R12, in which R11 and R12 are as defined above. xe2x95x90PR11.
m and n are identical or different and are zero, 1 or 2, m+n being zero, 1 or 2. m and n are preferably zero or 1.
The metallocenes described above can be prepared according to the following reaction scheme: xe2x80x83(Xxe2x95x90Cl, Br, I, O-Tosyl, HRa
xe2x80x83HRaxe2x80x94Rm8xe2x80x94R7xe2x80x94Rn9xe2x80x94RbH+2ButylLixe2x86x92LiRaxe2x80x94Rm8xe2x80x94R5xe2x80x94Rn9RbLi
Liraxe2x80x94Rm8xe2x80x94R7xe2x80x94Rn9xe2x80x94RbLi

It is especially preferred to use indenyl(h5-cyclopentadienyl) (dimethylsilyl)hafnium dichloride (=1) and indenyl(h5-cyclopentadienyl)(dimethylsilyl)zirconium dichloride (=2) as the metallocene compounds.
The activator is an aluminoxane of formula (II): 
for the linear type and/or of formula (III): 
for the cyclic type. In these formulae, R14 is a C1-C6-alkyl group, preferably methyl, ethyl or isobutyl, in particular methyl, and q is an integer from 2 to 50, preferably 10 to 40. However, the exact structure of the aluminoxane is not certain.
The aluminoxane can be prepared in a variety of ways.
One possibility is carefully to add water to a dilute solution of an aluminum trialkyl, the aluminum trialkyl solution and the water each being introduced in small portions into a larger amount of an inert solvent and the evolution of gas being allowed to finish between successive additions.
In another process, finely powdered copper sulfate pentahydrate is suspended in toluene and, in a glass flask. aluminum trialkyl is added, under inert gas at about xe2x88x9220xc2x0 C., in an amount such that about 1 mol of CuSO4.5H2O is available for every 4 A1 atoms. After slow hydrolysis with the elimination of alkane, the reaction mixture is left for 24 to 48 hours at room temperature, during which time it must be cooled, if necessary, to prevent the temperature from rising above 30xc2x0 C. The aluminoxane dissolved in the toluene is then isolated from the copper sulfate by filtration and the solution is concentrated under vacuum. It is assumed that, in this preparative process, the low-molecular aluminoxanes condense to form higher-molecular oligomers with the elimination of aluminum trialkyl.
Furthermore, aluminoxanes are obtained when aluminum trialkyl, preferably aluminum trimethyl, dissolved in an inert aliphatic or aromatic solvent, preferably heptane or toluene, is reacted, at a temperature of xe2x88x9220 to 100xc2x0 C., with aluminum salts containing water of crystallization, preferably aluminum sulfate. The volume ratio of solvent to aluminum alkyl used is 1:1 to 50:1xe2x80x94preferably 5:1xe2x80x94and the reaction time, which can be monitored by means of the alkane eliminated, is 1 to 200 hoursxe2x80x94preferably 10 to 40 hours.
Aluminum salts containing water of crystallization which are used in particular are those with a high content of water of crystallization. Aluminum sulfate hydrates are especially preferred, in particular the compounds Al2(S)4)3.16H2O and Al2(SO4)3.18H2O with the especially high contents of water of crystallization of 16 and 18 mol of H2O/mol of Al2(SO4)3 respectively.
Another variant for the preparation of aluminoxanes consists in dissolving aluminum trialkyl, preferably aluminum trimethyl, in the suspending agent, preferably in the liquid monomer or in heptane or toluene, previously placed in the polymerization kettle, and then reacting the aluminum compound with water.
There are other processes for the preparation of alumin-oxanes which can be used in addition to those described above.
Before it is used in the polymerization reaction, the metallocene can be preactivated with an aluminoxane of formula (II) and/or (III), which markedly increases the polymerization activity.
The preactivation of the transition metal compound is carried out in solution, the metallocene preferably being dissolved in a solution of the aluminoxane in an inert hydrocarbon. An aliphatic or aromatic hydrocarbon is suitable for this purpose. Toluene is preferably used. The concentration of the aluminoxane in the solution is in the range from approx. 1% by weight to the saturation limit, preferably from 5 to 30% by weight, based in each case on the total solution. The metallocene can be used in the same concentration, although it is preferably used in an amount of 10xe2x88x924-1 mol per mol of aluminoxane. The preactivation time is 5 minutes to 60 hours, preferably 5 to 60 minutes. The reaction temperature is xe2x88x9278xc2x0 C. to 100xc2x0 C., preferably 0 to 70xc2x0 C.
The catalyst to be used according to the invention is employed for the polymerization of 1-olefins of the formula Rxe2x80x94CHxe2x95x90CH2, in which R is an alkyl radical having 1 to 28 C atoms, preferably 1 to 10 C atoms, in particular one C atom, for example propylene, but-1-ene, hex-1-ene, 4-methylpent-1-ene or oct-1-ene. Propylene is especially preferred.
The polymerization is carried out in known manner in solution, in suspension or in the gas phase, continuously or batchwise, in one or more steps, at a temperature of xe2x88x9260 to 100xc2x0 C., preferably 0 to 80xc2x0 C. The pressure is 0.5 to 100 bar. Polymerization preferably takes place in the pressure range from 5 to 60 bar, which is of particular interest to industry.
The metallocene compound is used in a concentration of 10xe2x88x923 to 10xe2x88x927, preferably 10xe2x88x924 to 10xe2x88x926 mol of transition metal per dm3 of solvent or per dm3 of reactor volume. The aluminoxane is used in a concentration of 10xe2x88x924 to 10xe2x88x921 mol, preferably 10xe2x88x923 to 10xe2x88x922 mol per dm3 of solvent or per dm3 of reactor volume. In principle, however, higher concentrations are also possible.
If the polymerization is carried out in suspension or solution, the reaction is performed in an inert solvent conventionally used for the Ziegler low-pressure process, for example in an aliphatic or cycloaliphatic hydro-carbon; examples of such hydrocarbons which may be mentioned are butane, pentane, hexane, heptane, isooctane, cyclohexane and methylcyclohexane. It is also possible to use a naphtha or hydrogenated diesel oil fraction from which oxygen, sulfur compounds and moisture have been carefully removed. Toluene can also be used. Preferably, the monomer to be polymerized is used as the solvent or suspending agent. The molecular weight of the polymer can be regulated in known manner, hydrogen preferably being used for this purpose. The polymerization time is arbitrary since the time-dependent loss of polymerization activity shown by the catalyst system to be used according to the invention is only slight.
The process according to the invention is distinguished by the fact that the zirconium and hafnium compounds which are preferably used are very temperature-resistant, so they can also be used at temperatures up to about 90xc2x0 C. Moreover, the aluminoxanes used as cocatalysts can be added in a smaller concentration than hitherto. Finally, it is now possible to manufacture isoblock polymers at temperatures which are of interest to industry.
The following Examples will serve to illustrate the invention. The abbreviations used have the meanings given below:
VN=viscosity number in cm3/g,
Mw=weight-average molecular weight in g/mol,
Mw/Mn=molecular weight distribution determined by gel permeation chromatography (GPC),
II=isotacticity index determined by 13C NMR spectroscopy, and
niso=average length of the isotactic sequences.
Isoblock polymers can be detected and distinguished from other 1-olefin polymers by NMR spectroscopy with the aid of triple resonance analysis (q.v. A. Zambelli et al., Macromolecules 8, 687-689 (1975)). Markoff statistics are valid for isoblock polymers if the following equation is satisfied:
2(rr)/(mr)=1
The experimental results are collated in the Table.